147 research outputs found
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Modeling Temporal-Spatial Earthquake and Volcano Clustering at Yucca Mountain, Nevada
The proposed national high-level nuclear repository at Yucca Mountain is close to Quaternary faults and cinder cones. The frequency of these events is low, with indications of spatial and temporal clustering, making probabilistic assessments difficult. In an effort to identify the most likely intrusion sites, we based a 3D finite element model on the expectation that faulting and basalt intrusions are primarily sensitive to the magnitude and orientation of the least principal stress in extensional terranes. We found that in the absence of fault slip, variation in overburden pressure caused a stress state that preferentially favored intrusions at Crater Flat. However, when we allowed central Yucca Mountain faults to slip in the model, we found that magmatic clustering was not favored at Crater Flat or in the central Yucca Mountain block. Instead, we calculated that the stress field was most encouraging to intrusions near fault terminations, consistent with the location of the most recent volcanism at Yucca Mountain, the Lathrop Wells cone. We found this linked fault and magmatic system to be mutually reinforcing in the model in that dike inflation favored renewed fault slip
Severe hepatic trauma: a multi-center experience with 1,335 liver injuries.
The experience of six regional trauma centers with severe hepatic trauma was reviewed to identify trends in management, mortality, and postoperative complications. During the 5-year period ending June 1987, 210 complex liver injuries were identified at laparotomy. There were 92 Class III, 59 Class IV, and 59 Class V injuries. Mechanism of injury was blunt in 101 (48%) patients and penetrating in 109 (52%). Shock was observed in 38%, 46%, and 85% of Class III, IV, and V patients, respectively. Emergency department thoracotomy was performed in 31 patients. There was only one (3%) survivor. Resuscitative operating room thoracotomy was performed in 34 patients with three (9%) survivors. Class III injuries were most frequently treated with hepatotomy and individual vessel ligation (41%) and deep liver suturing (25%). Class IV injuries were most often managed by resectional debridement (36%). Class V injuries required caval shunt placement in 38 (64%) patients. There were only four (10%) survivors after caval shunt placement. There were 20 (59%) survivors of 34 patients treated with packing placed as an adjunct after hepatic injury repair. There was no significant increase in the incidence of abscess formation after perihepatic packing. Routine peritoneal drainage was used in 94% of patients. Overall mortality rates for Class III, IV, and V injuries were 25%, 46%, and 80%, respectively (p less than 0.01). Death rates due to the liver injury in Class III, IV, and V patients were 7%, 30%, and 66%, respectively (p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS
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Regional characterization of Western China
Geological, geophysical, and seismic data are being assembled and organized into a knowledge base for Western China as part of the CTBT Research and Development regional characterization effort. We have begun our analysis using data from the station WMQ of the Chinese Digital Seismic Network (CDSN). Regional seismograms are being analyzed to construct travel time curves, velocity models, attenuation characteristics, and to quantify regional propagation effects such as phase blockages. Using locations from the USGS Preliminary Determination of Epicenters (PDE) we have identified Pn, Pg, Sn, and Lg phases, constructed travel time curves, and estimated apparent velocities using linear regression. Surface wave group velocities will be measured and inverted for regional structure. Preliminary noise spectra for WMQ have been obtained from the IRIS DMC. Chinese seismicity catalogs from the USGS and SSB are being used to identify and obtain seismic data (including mine seismicity) and information for lower magnitude events. We have identified the locations of nearly 500 mines in China for inclusion in the knowledge base. Future work will involve expanding the data collection and analysis efforts to a larger region using data from additional CDSN, IRIS and portable stations
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